Spin polarization in quantum point contact based on wurtzite topological quantum well

Manipulating spin polarization in wide-gap wurtzite semiconductors is crucial for the development of high-temperature spintronics applications. A topological insulator revealed recently in wurtzite quantum wells (QWs) provides a platform to mediate spin-polarized transport through the polarization field-driven topological edges and large Rashba spin-orbit coupling (SOC). Here, we propose a spin-polarized device in a quantum point contact (QPC) structure based on ZnO/CdO wurtzite topological QWs. The results show that the QPC width can sufficiently control the lateral spin-orbit coupling (SOC) as well as the band gap of the edge states through the quantum size effect. As a result, the spin-polarized conductance exhibits oscillation due to the spin precession, which can be controlled by adjusting the voltage imposed on the split gate. The QPC-induced large spin splitting is highly nonlinear and becomes strong close to the gap. The spin splitting of the edge states will be suppressed for QPC widths greater than 50 nm, and thus lead to an extremely long spin precession length. This QPC width-dependent lateral SOC effect provides an emerging electrical approach to manipulate spin-polarized electron transport in topological wurtzite systems. The spin-polarized conductance in a wurtzite topological quantum well exhibits oscillation due to spin precession. The spin splitting of the edge states is suppressed for QPC widths of more than 50 nm, leading to a long spin precession length.

Automated summary

This article introduces a spin-polarized device based on ZnO/CdO wurtzite topological quantum well structure. By adjusting the width of the quantum point contact, both the lateral spin-orbit coupling and the band gap of the edge states can be controlled, resulting in spin-polarized conductance oscillation. When the QPC width is greater than 50 nm, the spin splitting of the edge states is suppressed, leading to an extremely long spin precession length. This approach provides a new electrical method to manipulate spin-polarized electron transport in topological wurtzite systems.